A battery cell has been proposed as a clean, efficient and environmentally responsible power source for electric vehicles and various other applications. One type of battery cell is known as the lithium-ion battery. The lithium-ion battery is rechargeable and can be formed into a wide variety of shapes and sizes so as to efficiently fill available space in electric vehicles. For example, the battery cell may be prismatic in shape to facilitate a stacking of the battery cells. A plurality of individual battery cells can be provided in a battery pack to provide an amount of power sufficient to operate electric vehicles.
Typical prismatic battery cells have a pair of plastic coated metal layers fused around a periphery of the battery cell in order to seal the battery cell components. The sealing of the battery cells generally begin with providing one of the plastic coated metal layers with a cavity, sometimes called a “butter dish” shape. The battery cell components are disposed inside the cavity of the plastic coated metal layer. The other of the plastic coated metal layers is then placed on top of the battery cell components and fused at the periphery to the one of the plastic coated metal layers with the cavity, for example, by heat sealing around the edges. The battery cell for incorporation in the battery pack is thereby provided.
Battery cells such as lithium-ion battery cells are known to generate heat during operation and as a result of a charge cycle when recharging. When overheated or otherwise exposed to high-temperature environments, undesirable effects can impact the operation of lithium-ion batteries. Cooling systems are typically employed with lithium-ion batteries to militate against the undesirable overheating conditions. Known cooling systems for battery cells are described in Assignee's co-pending U.S. patent application Ser. No. 12/713,729 to Essinger et al. and U.S. patent application Ser. No. 12/842,478 to Kumar et al., the entire disclosures of which are hereby incorporated herein by reference.
Conventional cooling systems have included cooling plates or fins sandwiched between individual battery cells within the battery pack. The cooling fins are typically joined by “hot” methods such as brazing or welding to a heat sink. Hot joining methods can undesirably affect material microstructure, which can affect joint durability. Known joining methods also typically require filler material such as brazing solders, welding consumables, bonding adhesives, and thermal interface materials, which can undesirably affect thermal conductivity and increase manufacturing complexity.
There is a continuing need for a battery cooling system and a method for making the same that maximizes a durability at joints of the battery cooling system. Desirably, the battery cooling system and method does not require filler materials, facilitates a thermal conductivity from adjacent battery cells, and has a minimized manufacturing complexity.